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Coming back to pedestrian crossings - I encountered this spot recently and it blew me away - I didn't know these existed, but it's such a simple solution to the problem. This is a pedestrian crossing of a six-lane undivided roadway, with heavy traffic, at an unsignalized intersection. The solution is to put little flag-holders with about 10 slots and 5 flags on each side of the intersection. There are signs (unfortunately facing away from the intersection) telling people how to use it. You pick up the flag, and stick it out while still standing safely on the curb, and wait for the traffic on your left to stop. Then you start proceeding, making sure the other direction of traffic stops too. It's amazing how much faster the driver response is with an orange flag - it's absolutely clear that your intent is to start crossing the roadway. It's also nice because the parked cars can obscure the pedestrians at this location - so the flag helps you be seen without exposing yourself to traffic. I'm curious how often the flags need replacing (and / or just being ferried back to the side with less demand - you can see in this photo almost all the flags are on the west side - but smart helpful pedestrians can help out by taking a handful with them). Overall seems like a nice low-cost alternative to a HAWK Beacon. Anyone have experience with these? http://maps.google.com/maps?q=Conne...159.38,,0,10.21
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Sep 17, 2012 20:20
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SlothfulCobra posted:How do you decide if a shopping center is worthy of a traffic light? The Manual on Uniform Traffic Control Devices spells out 9 "warrants" which are cases where installing a traffic light would be appropriate. For a shopping center, it would probably be one of the first 4 warrants, for vehicle or pedestrian volumes. http://mutcd.fhwa.dot.gov/htm/2009/part4/part4c.htm Warrant 1, Eight-Hour Vehicular Volume Warrant 2, Four-Hour Vehicular Volume Warrant 3, Peak Hour Warrant 4, Pedestrian Volume Warrant 5, School Crossing Warrant 6, Coordinated Signal System Warrant 7, Crash Experience Warrant 8, Roadway Network Warrant 9, Intersection Near a Grade Crossing
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Dec 18, 2012 15:08
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Jonnty posted:They're not reflective apaprently - reflective ones are, at least in the UK, called cat's eyes. Retroreflective! The light returns in the same direction it came from - otherwise your headlights would just be lighting up other things that aren't your eyeballs. And as a neat fact, many (all?) jurisdictions, as they paint roadway lines, they drop a layer of glass beads into the wet paint. The tiny half-submerged spheres are retro-reflective, so when your headlights hit them, extra light bounces straight back towards you (making it visible to you) instead of just bouncing off down the road away from you. Properly maintained road signs are also retroreflective - which is why new ones can seem so blinding when your headlights hit them. As they fade over time, patches of them lose their retroreflectivity, and you get weird patterns of darkness on signs.
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Mar 12, 2013 20:45
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mamosodiumku posted:Are there rules for how a utility should repave a road after they dig it up? The quality of the repaving seems to vary drastically. There's one spot where there are tire marks on the section of road they filled in. The contractor generally has a set of specifications that he is required to perform the work in accordance with - these outline the materials, compaction requirements, durability, etc. for the patching. If the utility patch is rutting, he probably didn't do it right. Report it to the entity that owns and maintains the road (State, County, local). If it's soon enough after the work was done, they may force the contractor to fix it at his own cost - otherwise they may just fix it themselves. If you're unsure what entity owns the road, I would report it to the higher one - they'll probably be best about telling you "no, this is a County road".
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Jun 15, 2013 15:56
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snickles posted:So, can you explain what's going on here? At first blush, this looks a little dicey, but the cloverleaf interchange actually interacts with collector/distributor roads on I-10, so it's not so unreasonable. Ditto the other new entrances / exits. And it's not actually even a full cloverleaf, since there's no weave present for the northeast quadrant. And like you said, the northwest quadrant of the cloverleaf (if property connected, looks like an oops) would act only as a U-turn for traffic going from NB I-110 to SB I-110.
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Jun 21, 2013 15:13
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Cichlidae posted:I made a diagram of the volumes on I-91 NB. Full PDF is here. It would be really fun to put a spreadsheet together to convert excel traffic volumes into a Microstation script to draft the volume line on that graph. Assuming you otherwise do it manually, and that it's not created by some other automated program.
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Jun 28, 2013 16:07
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PittTheElder posted:
They already have a ferry! I was wondering how much longer the trip would take, and when google took me across the bay I was assuming that it was doing one of those cute "kayak across the pacific" things. But nope, ferry. Between two random points in the cities, it's 182 km and 8 hrs with the ferry. If you avoid the ferry, it's 1411 km and 16 hrs.
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Jul 14, 2013 19:39
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Is that really easier than just making a big old ferry line?
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Cichlidae posted:Q: What takes two weeks to make and looks awesome? Color code the ADT line by level of service!
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Aug 8, 2013 22:52
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Presto posted:Reminds me of that one Douglas Adams book where the guy was writing a program to turn natural rhythms into music. I suspect the Washington, DC area traffic would not be soothing. The Beltway is farting again 
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Aug 10, 2013 02:08
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Cichlidae posted:Boy guys, I think I spotted a little problem out in the field: I'm a bit confused as to what I'm supposed to be seeing here. The black tire marks are surely construction traffic from soon after the paving was completed, yes? It's tempting to think those are skid marks, but that doesn't really make sense. The ones moving from the shoulder to the main line in particular - that would be someone accelerating / laying down rubber, which just seems impossible. If it was an emergency stop it wouldn't keep continuing. And the short little wavy tracks are likewise probably a truck that drove off of the hot asphalt, picking up some asphalt binder on the tires, then it sat there a while and the asphalt cooled, then it drove off. Someone slamming on the brakes wouldn't be able to create such fast back-and-forth skid marks. Is the picture just showing all that new pavement real estate that was meant to be accel / taper instead of full width shoulder? Don't you need healthy amounts of full width shoulder at the end of your accel anyway? It's hard to tell from the picture and without plans, but if I had the choice of ending a taper before I hit that curve, or tapering through that curve, with inadequate shoulder immediately past it, I think I would end the taper earlier. Especially if it's an existing condition that people have gotten used to working with.
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Sep 10, 2013 20:59
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Washington DC has been using Beet Juice to pre-treat roadways (so sugar lowers the freezing point instead of a salt). And funny story, they train their engineering staff to drive the beet-juice sprayers / snow plows. Sorry, we'll have to postpone the meeting - the PM was up all night plowing the roads.
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Sep 17, 2013 16:57
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Haifisch posted:That said, not all designers seem to really "get" them: Somewhere, the guy who wrote the section of the MUTCD on signing roundabouts is drinking himself into a stupor over those signs. It's like they were having trouble with people using the roundabouts and they just kept throwing more poo poo at it.  :How about a stop sign! No, now they're turning left - we'll add one way signs! And Right Turn Only signs in the left lane! What do you mean now people are getting in the left lane to take the first exit of the roundabout? gently caress it, let's put the signal back in.
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Sep 27, 2013 03:39
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Grundulum posted:Thanks for the serious answer to a half-joking question. I still don't understand what's difficult about that sign, but I think I have an occupational bias towards not understanding why others don't understand. Clear zone is a concept discussed in the Roadside Design Guide, and is measured horizontally from the edge of the travel lane. Its width varies depending on the speed and traffic volume of the roadway. It's basically a "Don't put poo poo in here that will kill people if they hit it at speed, because out of control vehicles have a good chance of hitting it" zone.
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Sep 27, 2013 23:57
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PittTheElder posted:Link? I'm not sure I know what you're referring to. At least I can't picture it. Various flavors of these badboys: https://www.google.com/search?q=truck%20mounted%20attenuator
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Sep 30, 2013 05:08
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Koesj posted:Don't fret, with the new A27 project coming up I'm sure they'll find a way to 35% Roadway Review Comments: Make the loop ramps look like testicles 65% Roadway Review Comments: No, one of mine hangs a LOT lower than the other one. 90% Roadway Review Comments: Perfect!
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Oct 10, 2013 00:50
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Baronjutter posted:Don't things you can crash into near the sides of the road generally reduce speeds and force people to drive more carefully? I know where I live they're always trying to narrow roads and plant trees or add street parking to help reduce speeds and get people more alert. Is every road supposed to have a 500m field of soft foam around it or something? Slowing speeds by narrowing the roadway corridor is a thing - but it's primarily intended for low speed roadways. Curbs are not considered an obstacle - and if you were going to plant something in the clear zone, it would hopefully be landscaping or shrubs that aren't considered obstacles, but still give you a feeling like the corridor is cramped. This spot isn't the best example due to the planting of trees within the clear zone (in areas w/o guard rail - the rail is there protecting the side slope), but driving it in person really does make you drive slower than if that flat curve were wide open.
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Oct 15, 2013 18:08
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Baronjutter posted:I guess I don't understand why that monument is a problem but all the lamps and telephone poles and such right by the curb aren't. The little monument seems way farther from the edge of the road than buildings usually are along the street. A building 6' from the curb is ok, a lamp a foot from the cub is ok, a little monument 10' from the curb is a horrible danger. Lamps are designed to be "breakaway". The bolts that attach it to the ground are engineered to shear off when they get hit hard enough. The Roadside Design Guide has an exception for trees and utility poles, because it acknowledges that you can't always get them far enough away. You try to, though. And both light poles and utility poles are there to serve a purpose - the monument is decorative, and could be made out of something breakaway and/or moved into a safer spot outside the clear zone. You are less likely to see newly planted trees in the clear zone - and with old trees, it's hard to have the political will to cut down an existing enormous tree just for safety improvements. In some cases you might not win the fight with the environmental agency whose responsibility it is to protect the trees.
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Oct 15, 2013 19:27
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Baronjutter posted:Here the "street tree lobby" or what ever you call it is way too powerful for that to ever happen. Also the city has a pretty progressive stance on roads. I can't remember the last time they ever expanded a road, but they love removing lanes, widening sidewalks, adding bike lanes, road diets, entire road closures. So here the monument example the problem would be that cars might damage it, so lets remove 2 of the 4 lanes, expand the median into a proper little park, and add some bike lanes and cut the speed limit down a notch. And plant some nice oaks or chestnuts around the perimeter to protect people in the park from the evil cars. Also add a signaled crosswalk leading pedestrians through a pleasant path around the monument. Put up w-beam guardrail to protect the monument, call it a day 
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Oct 15, 2013 20:12
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smackfu posted:Is there some city traffic philosophy that basically says "no protected left turns, and no left turns at all during busy times." We saw a lot of that in San Francisco and it really screwed up the GPS. To have a protected left turn phase, you generally need a dedicated left turn lane, which is room that could otherwise be used for shoving more through lanes in. So If you have enough room for sidewalks, parking lanes, and two through lanes in each direction, you just don't have room to make a protected left turn work. Which is why you often end up with permissive lefts, and then when rush hour rolls around you have to prohibit the left turn, because otherwise someone will wait there and block the through lane.
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Oct 17, 2013 13:33
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mamosodiumku posted:When you design a turn, do you usually try to keep it so it has a constant radius? Are there situations that may warrant changing how tight a turn is mid turn? There's several ways you can do horizontal curves: Tangent - Curve - Tangent: This is the typical way that we do curves in Maryland. It's easy to lay out during design, keeps it simple during construction. Spirals: Some jurisdictions use spirals - North Carolina, for instance. These are kind of like variable-radius curves that help you transition smoothly into and out of the curve. The idea is that this recognizes that drivers turn the wheel non-instantaneously, so it better matches the car's real path. It's also more pleasing to the eye. Compound Curves: Sometimes due to the surrounding features or topography, it's desirable to use compound curves. A compound curve is when you have two curves going in the same direction back to back. AASHTO says that the ratio of the radii not exceed 1.5:1 - so you could have 600' radius into 900' radius. Reversing Curves: These are somewhat unusual, because roadway curves are superelevated (think the banking at a circular racetrack), and when you have reversing curves it can be difficult to make this work correctly. You would typically have a short section of tangent between the reversing curves in order to allow for the superelevation transition. Broken Back Curve: This is what you DON'T do. You never want to have two curves in the same direction separate by a tangent. This is because it violates driver expectiations, and causes crashes. Similarly, you wouldn't use compound curves going lowradius-higherradius-lowradius, even if it met the 1.5:1, because of the same problem - confuses drivers, causes crashes.
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Oct 19, 2013 22:37
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While I agree that we need to tax the poo poo out of everyone and build a socialist utopia, the correct answer is to reevaluate your cutoff so that it tells you to build left turn lanes roughly where you were before. Can't rock the boat.
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Oct 23, 2013 00:23
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Entropist posted:Is that really a source of conflict? Cyclists are flexible, when you see that a car has their right turning signal on, you can go wait on the left side instead to avoid getting in the way. That's how people do it in the Netherlands anyway. Ah yes, we'll just depend on Americans being conscientious and self-aware. I'm pretty sure the AASHTO bike guide has a section on assuming that cyclists and drivers are engaged in a blood feud.
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Oct 29, 2013 23:53
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Armacham posted:I was visiting my parents in the Phoenix, and took my sister to the movies. I think I discovered the worst intersection in Metro Phoenix. What's wrong with those roundabouts?  I know our traffic guys don't like doing the bypass lanes around the roundabout, but for what would otherwise be a three-lane roundabout those don't look so bad.
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Nov 4, 2013 14:32
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Armacham posted:1. People in phoenix don't know how to use them, which leads to : How are people mis-using them? Is the traffic in the circle trying to yield to the approaches? I'm always curious to hear anecdotes for how designs can get fouled up during real operations. It may just be that the intersections are undersized for the actual traffic volumes.
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Nov 4, 2013 15:12
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Baronjutter posted:It's apparently still safer to have them on the streets. You're far more likely to be hit by a car by riding on the sidewalk than on the street. Cars aren't excepting something moving almost as fast as them darting off a sidewalk at an intersection, or when they're backing out of their driveway. Also there's just no room, you'd need double-wide sidewalks. I've been in places in europe that have the bikes on sidewalks sometimes and it works out ok because people are used to it and the sidewalks are marked but it's still a pain because pedestrians are constantly getting in the way. They also sort of go on to the street at intersections to be more visible. Fast moving bikes can also straight up injure people, or worse. There was a case of someone on an off-road trail in DC blowing past an older woman from behind, warning her "on your left". She apparently didn't understand the convention because she moved left, got hit by the cyclist, and died of her injuries.
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Nov 4, 2013 20:51
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The idea of messing with different traffic modes to increase the feeling of personal safety is interesting. Baltimore is actually removing several 2nd-story pedestrian bridges connecting buildings downtown, partly because they made people feel unsafe, both below and above - they're trying to make it have more foot traffic on the street level to feel safer, even if it does mean more effort in crossing the street.
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Nov 9, 2013 21:46
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Consist posted:Is this an innovative way of solving the problem or is this an accident waiting to happen? It can be both  Other things you can do at a dog-leg that's lined up the "wrong" way like this: Eliminate some of the movements - make one of the legs right-in-right-out Re-align the intersection so it's actually an intersection
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Nov 13, 2013 00:24
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For anyone interested in bike applications, check out the NACTO Urban Bikeway Design Guide, available for free on the internet: http://nacto.org/cities-for-cycling/design-guide/ It's pretty comprehensive about detailing the various shalls, shoulds, and options of design features. It has diagrams of the second method Carbon Dioxide mentioned (Two Stage Turn Queue Boxes).
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Nov 15, 2013 21:19
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I worked with a guy who went on a bike ride on an off-road asphalt path after it had rained. His wife went looking for him when he didn't come back - and found him unconscious, having fallen from his bike, not wearing a helmet. He had brain damage, and a year after the accident was able to walk again, and a couple years after he was able to drive short trips in the car. But he will never be able to work as an engineer again. I went through college not wearing a helmet, but after seeing how it can ruin your life, I sure as hell do now.
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Nov 20, 2013 17:16
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will_colorado posted:Cichlidae, does that appear to be ghost ramps for a stack interchange here? I think those two "extra" ramps inside are added so that you can separate the weaving movements from the southbound 470 traffic. You'll notice that you can actually make the weave from the west side of the cloverleaf to/from southbound 470. Edit: Ditto for those internal ramps on EB Pena
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Dec 4, 2013 05:29
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Qwijib0 posted:I'd find it unsettling to not see reverse direction traffic at least once every half mile or so, especially on an unfamiliar road. Reassurance that yes, there is a way back is comforting, both for returning from a destination or needing to backtrack because of a mistake. I think you're close to the answer. If I drive up a route, it would be nice to be able to recognize that I'm on the same road while I'm coming back the other direction. Particularly in a time before GPS / smartphones were ubiquitous. As a second guess, maybe to allow for future maintenance of traffic median crossovers if something happens like a bridge has to be closed unexpectedly.
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Dec 11, 2013 01:46
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Mandalay posted:Costco sells bridges so I can't see how this would fail. http://www.costco.com//.product.115...content=Default 2'-11" width does not meet AASHTO recommendations for minimum width. It apparently does meet the AASHTO requirement for uniform pedestrian loading of 85 lbs/ft2, which I was surprised at. Although I doubt the typical installation method of "mow grass, place bridge" will let it support that 1800 pounds.
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Dec 11, 2013 19:39
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Cichlidae posted:Maybe I should have clarified: ROW is right-of-way. I'm working on a small sidewalk job where we took out the buffer between the curb and the sidewalk in some locations because it was in front of people's houses, and didn't want to impact their yards too much. Except it's not! There's like 20' of additional room within the ROW there, it's just that people treat it like their yard, and put in landscaping/walls.  It's like some weird adverse possession where if you put up a fence, local governments will be afraid to challenge you on it.
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Dec 14, 2013 19:07
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Ryand-Smith posted:So, I have been traveling through a lot of bridge tunnels recently, and I have noticed the tunnel portions have 2 sets of lights. Is this a normal thing for tunnels, or just a wierd VDOT thing that they do with bridge tunnels. What do you mean by a bridge tunnel? Do you mean a tunnel on land, as compared to a normal tunnel under a body of water? Like this cut-and-cover tunnel on MD 200: https://maps.google.com/maps?q=icc&....31&hq=icc&z=17 Tunnels in general need lights to see, somewhat obviously. The tunnel lights need to be pretty bright sometimes, because if you drive into a tunnel during a sunny day, your eyes can't adjust to dim "normal night-time" lighting. So for tunnels, you might need more lights to provide adequate light levels.
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Dec 15, 2013 23:52
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Ryand-Smith posted:https://en.wikipedia.org/wiki/Chesapeake_Bay_Bridge%E2%80%93Tunnel Looks normal for a tunnel. The lights are designed to give a consistent pattern to avoid light-dark-light-dark patterns, and with enough intensity that the transition from outside to inside to outside doesn't screw with your vision too much. Long strings of lower-intensity lights like they're using may also be better for redundancy's sake, since getting a lane of the tunnel shut down for maintenance would be annoying. https://maps.google.com/maps?q=Ches...,222.55,,0,-2.1
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Dec 16, 2013 00:34
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Peanut President posted:Hahah you wanna see dumb pedestrians? Here in Evansville we have a casino on a boat in the river. The company (Tropicana now but Aztar before) has a hotel across Riverside Drive, a four lane boulevard. So they built a bridge that goes between the hotel and the riverboat, to make it easier on people to get to it. As far as I know you can just walk from the parking garage to the bridge without having to rent a room. Everytime I'm down there I see at least 1, usually 4 or more, people walking right in the middle of the road, DIRECTLY UNDERNEATH the pedestrian bridge. Pedestrian bridges are notoriously hard to get people to utilize. The AASHTO Pedestrian Guide has a graph of empirical data of utilization rate vs. time savings - basically unless you get *significant* time savings, people won't use them. And once you factor in how far out of your way you have to go, bridges can become infeasible pretty quickly. Weirdly, tunnels get used at higher rates for the same time savings.
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Dec 17, 2013 23:24
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drunkill posted:It is easier to walk down into a tunnel instead of up over a bridge! Just take one of the two elevators we would be required to place at either end of the bridge or tunnel. Can't just have one, because their maintenance staff is poo poo, and they would get in trouble with no working elevators.
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Dec 18, 2013 04:27
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The Deadly Hume posted:The tunnel preference is weird to me because I usually associate ped tunnels with getting mugged. Can also happen on a bridge too of course but they have exposure. I think Qwijibo's comment about not wanting to take the stairs is actually on the mark - despite both options having stairs to take. If you are faced with a set of stairs going up, you're more likely to say "gently caress it, I'll wait". If you start with the easy down stairs, you're already locked in and can't change your mind. 
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Dec 18, 2013 06:12
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altazakin posted:I have an intersection near me that has been bugging me for a long time. There is a left turn lane with a left-turn arrow light at a stoplight on a road near me. There is no road on the left, only the right. There are houses and driveways on the left but who would get their own private drive left turn lane? The light is decently newish, it is newer than the houses there, which were built in the late 50s/early 60s. There was never a road to make a left turn onto. So what is the lane and signal for? I don't know if posting the intersection is allowed. Here is a bunch of pics from different angles. There is no road behind the house, it is a canal with a paved footpath. http://imgur.com/a/oyBP5 Any ideas? Can someone just bug the city enough to get their own left turn signal and lane? In the first photo, if you look just a little upstream you can see that that center lane is marked as a two-way left turn lane, so the lane part of the question is that the pavement and lane width was already there, the pavement marking left turn arrow just clarifies that it's a left turn lane at the intersection. As far as the left signal arrow, that does seem like overkill. But if the signal has a sensor so that it doesn't fire off unless necessary, it wouldn't negatively effect operations. It probably is a case of the squeaky wheel getting the grease - perhaps when they were designing that intersection, they needed to acquire some property from that homeowner, and he asked for that as a condition of selling.
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Dec 26, 2013 21:22
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SurgicalOntologist posted:Not sure if this will work, can't figure out how to get a direct street view link: To put in a signal, the intersection must meet one of the warrants from the MUTCD listed here: http://mutcd.fhwa.dot.gov/htm/2009/part4/part4c.htm If they put in a signal that didn't meet one of those warrants, and there was an accident (for example a rear-end collision for someone stopped at the light), it would be more difficult for the engineer to defend against a lawsuit [You put in a light where there shouldn't have been one!]. Note that Warrant 7 is for crash history - but it still requires a couple other conditions before it would be warranted.
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Dec 27, 2013 23:43
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